Determination of processing maps for the warm working of vanadium microalloyed eutectoid steels

摘要

Microalloying of an eutectoid steel with V may facilitate formation of dispersed nano-scaled VC particles in the microstructure during thermomechanical processing or subsequent heat treatment In this research, the constitutive flow behavior of vanadium microalloyed eutectoid steel has been investigated in the temperature range 620-770 ℃ at strain rates in the range 0.01-10 s~(-1). Microstructural characterization of the deformed specimens was conducted using SEM and EBSD techniques. In this context, various deformation mechanisms occurring during warm deformation have been characterized and delineated through construction of a processing map by establishing a power dissipation map and an instability map for the steel and superimposing them. The results show that the pearlitic microstructure exhibits several deformation mechanisms within these warm working conditions. Dynamic spher-oidization of cementite lamella takes place in the range 660-720 ℃ and 0.01-0.1 s~(-1) with a power dissipation efficiency of 27-33%, characterizing a safe window of processing this steel. The presence of vanadium carbides at grain boundaries strengthened the pearlitic microstructure and retarded the occurrence of some deformation defects during low temperature, high speed deformation in the range 620-720 ℃ and 1-10 s~(-1).